AGGREGATION OF PERCHLORATES IN APROTIC DONOR SOLVENTS .1. LITHIUM ANDSODIUM PERCHLORATES

Non-aqueous solutions of lithium and sodium perchlorates have been inv estigated by IR and Raman spectroscopy. The (ClO4)-Cl-35, and (ClO4)-C l-37 isotopomers induce an asymmetry or a splitting of v(3) and v(4) b ands. All spectra are interpreted by assuming that the bands of possib le solvent-separated species are at the same wavenumbers as if they we re free ions ('spectroscopically free ions'). In ionizing solvents (di methylsulfoxide, N,N-dimethylformamide, acetonitrile or acetone) these perchlorates are partly or completely dissociated into free ions whil e in associating solvents (esters, cyclic ethers or nitromethane) LiCl O4 is in part dimerized. In nitromethane, LlClO(4) ion pairs are sligh tly dissociated into free ions at low concentrations and dimerized at high concentrations. The coordination of ClO4 in the ion pairs is eith er monodentate (LiClO4) or bidentate (NaClO4). Both ClO4 groups in the LiClO4 dimer are linked by two lithium bridges into a centrosymmetric al structure.